The present invention relates to an ink composition for a meltable ink usable in a printing apparatus in which ink droplets are ejected from ink ducts. The present invention also relates to an ink composition for a meltable ink usable in a printing apparatus, said composition containing a meltable base material. The present invention also relates to a number of esters derived from 2,2'-biphenol.
Ink compositions are well known, for example, from U.S. Pat. No. 5,122,187. However, such ink compositions generally result in printed ink layers which are either too brittle or too soft on the receiving materials, so that the gum, scratch and fold resistance (GKV), particularly of the different ink layers of different colors disposed on one another is inferior.
In order to toughen ink formulations which are too brittle or to stiffen crystalline materials which are too soft, it is necessary to use an amorphous binder. After the cooling of the melting ink composition the printed images are then less vulnerable. The amorphous state also ensures good light transmission, this being favorable for color fastness and use on overhead sheets.
It is known from U.S. Pat. No. 5,421,868 that these amorphous binders can considerably increase the viscosity of the ink in the melted state, this being a disadvantage with respect to the operation of the printing apparatus. For this reason it is preferred to use binders which contain monomer compounds.
It is well known that monomer compounds, e.g. waxes, are generally crystallizable. The purer the compound and the lower the molecular weight, the easier it is to form a crystal lattice. However, binders are known which contain monomer compounds, which, when used in an ink composition for a printing apparatus, solidify amorphously on the receiving material. If an ink provided with such binders is printed on a receiving material, said binders admittedly form an amorphously solidified phase, but in the course of time they will exhibit partial after-crystallization. The result is that the properties of the printed layer change so that the gum, scratch and fold resistance decreases, the color impression changes and the transparency is reduced.